Plastic materials for the production of deep-drawn films

ABSTRACT

Plastic compositions for the production of deep-drawn films have the following composition: 
     
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                         Parts By Weight                                       
______________________________________                                    
Polyvinyl chloride    35-40                                               
Acrylate rubber/PVC (1:1)                                                 
                      40-50                                               
Plasticizer            5-10                                               
Acrylate rubber/Styrene (3:1 to 7:3)                                      
                       0-15                                               
Polystyrene/polyethylenebutylene                                          
                       0-10                                               
block copolymer                                                           
Processing agents     4-5                                                 
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     The plastic film products from these materials have a high degree of strength and resistance to aging. Inhomogeneities and hard particles in the films are eliminated.

The invention relates to plastic materials for the production of deep-drawn films, as for flexible packaging. This application is a continuation-in-part of Ser. No. 861,154 filed May 8, 1986, now abandoned.

A number of deep-drawn films based on polymer mixtures are known that use polyvinyl chloride (PVC). The properties of such films, however, are not satisfactory with respect to resistance to aging and strength, especially under thermal stress.

Plastic materials based on ethylene vinyl acetate (EVA) or polyethylene (PE) tend during deep drawing to form "flecks" (i.e. hard spots) or undissolved particles of higher molecular weights or cross-linked resin. Ethylene vinyl acetate cannot be brought to a fluid form, particularly with high content of vinyl acetate (about 70%).

The object of the present invention is to provide plastic materials that can be easily drawn into films, whose properties are improved, especially with regard to strength and resistance to aging. The invention permits the ingredients to be mixed efficiently and simply in a heated vessel, and subsequently calendered or extruded into films.

The plastic materials for achieving the objective of the invention have the following composition:

(a) 55-65 parts by weight polyvinyl chloride;

(b) 50-60 parts by weight acrylate rubber;

(c) 0-10 parts by weight styrene;

(d) 0-10 parts by weight polystyrene/polyethylene-butylene block copolymer;

(e) 5-10 parts by weight plasticizer; and

(f) 4-5 parts by weight processing agents.

These plastic materials are characterized by improved workability, enhanced strength and improved resistance to aging.

In a preferred composition the polyvinyl chloride takes the following form and the acrylate rubber is incorporated in admixture with PVC and styrene as follows:

(a) 35-40 parts by weight S-PVC dispersion resin with a K value of about 60;

(b) 40-50 parts by weight of a mixture of acrylate rubber and PVC; and

(c) 0-15 parts by weight of a mixture of acrylate rubber and styrene.

Preferably, the mixture ratio of acrylate rubber to PVC=1:1 in (b) above and the ratio of acrylate rubber to styrene=3:1 to 7:3 in (c) above.

S-PVC represents PVC that has been formed by suspension polymerization. This is, the monomer or mixture of monomers is dispersed by mechanical agitation in a second liquid phase in which both the monomer and polymer are essentially insoluble. The resulting polymers may be in the form of pearls, beads, soft spheres or irregular granules which are easily spearated when agitation is ceased.

The normally used processing agents are utilized preferably in the following composition:

(a) 2 parts by weight SnS (stabilizer);

(b) 0.3 parts by weight partly oxidized polyethylene wax;

(c) 1 part by weight tris(hydroxyethyl) isocyanurate;

(d) 0.3 parts by weight tris(nonylphenyl) phosphite; and

(e) 1 part by weight octadecyl 3-(3.5-4 hydroxyphenyl propionate).

Some examples of plastic materials that can be worked into films are given below.

A special advantage of the plastic materials according to the invention is that they can be transformed into purlable forms, which is not possible with ethylene vinyl acetate (e.g., the commercial product Levapren). This considerably facilitates the production of films.

                  TABLE                                                            ______________________________________                                                         Example                                                        Ingredient        1      2      3    4    5                                    ______________________________________                                         S-PVC dispersion resin with K                                                                    35     35     40   40   35                                   value of about 60                                                              Epoxidized fatty acid ester                                                                      5      10     5    10   5                                    plasticizer                                                                    Acrylate rubber/PVC (1:1)                                                                        50     50     40   40   50                                   Acrylate rubber/styrene (3:1)                                                                    10     5      15   10   --                                   Polystyrene/polyethylene-                                                                        --     --     --   --   10                                   butylene block copolymer                                                       Processing Agents                                                              SnS stabilizer    2      2      2    2    2                                    Partly oxidized polethylene wax                                                                  0.3    0.3    0.3  0.3  0.3                                  Tris(hydroxyethyl) isocyanurate                                                                  1      1      1    1    1                                    Tris(nonyphenyl) phosphite                                                                       0.3    0.3    0.3  0.3  0.3                                  Octadecyl 3-(3.5-4 hydroxyphenyl                                                                 1      1      1    1    1                                    propionate)                                                                    ______________________________________                                    

Acrylate rubbers are thermoplastic polymers consisting largely of one or more esters of acrylic acid such as ethyl acrylate and butyl acrylate. Since acrylate rubbers have no double bonds, they are very resistant to aging, heat, fatigue, oxygen, ozone, oil and ultraviolet light.

Other suitable plasticizers are trimellithate esters of aliphatic alcohols having 6 to 12 carbon atoms e.g., 2-ethylhexyl trimellithate.

From plastic materials in examples 1-5, strips were made and their elongation at break and permanent sets measured in the delivery state, as well as after a heat treatment and exposure to a xenon lamp. The results are given in Table II below.

                                      TABLE II                                     __________________________________________________________________________                            Elongation        Permanent                                                    At Break          Set (%)                                    Elongation                                                                           Elongation  After 500                                                                            Permanent   After 500                                  At Break                                                                             At Break    hrs. xenon                                                                           Set (%)     hrs. xenon                                 Delivery                                                                             After 500   lamp test                                                                            After 500   lamp test                                  Condition                                                                            hrs. 120° C.                                                                        exposure                                                                             hrs. 120° C.                                                                        exposure                              Example                                                                             Lengthwise                                                                           Lengthwise                                                                           Lengthwise                                                                           Lengthwise                                                                           Lengthwise                                                                           Lengthwise                                                                           Lengthwise                            __________________________________________________________________________     1    x = 170                                                                              x = 160                                                                              x = 170                                                                              x = 170                                                                               94   100   100                                        s = 10                                                                         n = 5                                                                     2    x = 180                                                                              x = 160                                                                              x = 170                                                                              x = 170                                                                               89    94    94                                        s = 11                                                                         n = 5                                                                     3    x = 160                                                                              x = 170                                                                              x = 170                                                                              x = 160                                                                              106   106   100                                        s = 3, 9                                                                       n = 5                                                                     4    x = 170                                                                              x = 170                                                                              x = 160                                                                              x = 170                                                                              100    94   100                                        s = 5                                                                          n = 5                                                                     5    x = 190                                                                              x = 200                                                                              x = 190                                                                              x = 170                                                                              105   100    89                                        s = 9                                                                          n = 5                                                                     __________________________________________________________________________      x = average value                                                              s = variation                                                                  n = number of samples                                                    

The permanent set is a characteristic indicative of the life or aging resistance of the plastic material. The permanent set after 500 hours 100° C. should be above 50% and the permanent set after 500 hours xenon test exposure should be above 67%. The prior art plastic materials suitable for deep drawing do not reach these values.

The plastic materials according to the invention contain no plasticizing agent on the basis of ethylene vinyl acetate or olefin terpolymers. The films produced from the plastic materials of the invention have no inhomogeneities and no hard flecks or particles.

The plastic materials according to the above mentioned compositions are preferably produced as follows:

EXAMPLE 1

35 parts by weight S-PVC are stirred and heated up to 120° C. in a heating vessel and while maintaining stirring, 5 parts by weight of a epoxidized fatty acid ester plasticizer, 2 parts by weight SnS stabilizer and 0.3 parts by weight tris (nonylphenyl) phosphite are added to obtain a first homogenized mixture. The homogenization time will be about 5 minutes. Then this mixture is cooled to room temperature to obtain a purlable, sandy product also called "dryblend". Thereafter to this mixture are added the further ingredients of the recipe, i.e. 50 parts by weight acrylate rubber/PVC (1:1), 10 parts by weight acrylate rubber/styrene (3:1), 0.3 parts by weight partly oxidized polyethylene wax, 1 part by weight tris(hyodroxyethyl) isocyanurate and 1 part by weight octadecyl 3-(3.5-4 hydroxyphenyl propionate). The ingredients are constantly stirred within said vessel or a mixer until a second homogenized mixture is obtained. From this second homogenized mixture there are produced films by the well-known calendering or extrusion process.

EXAMPLE 2

35 parts by weight S-PVC with a K value of about 60 are heated up to 120° C. under stirring in a heating vessel and are mixed during further stirring with 5 parts by weight of 2-ethylhexyl trimellithate plasticizer, 2 parts by weight SnS stabilizer and 0.3 parts by weight tris(nonylphenyl) phosphite until a first homogenized mixture is obtained. Homogenization takes about 5 minutes. This first homogenized mixture is then cooled down to room temperature thus giving a purlable, sandy product which is a dryblend. Then there are added to this mixture in said heating vessel or in a mixer, the further ingredients of the recipe:

40 parts by weight acrylate rubber/PVC (1:1), 10 parts by weight polystyrene/polyehtylene-butylene block copolymer, 0.3 parts by weight partly oxidized polyethylene wax, 1 part by weight tris(hydroxyethyl) isocyanurate, 0.3 parts by weight tris(nonylphenyl) phosphite and 1 part by weight octadecyl 3-(3.5-4 hydroxyphenyl propionate). Maintain stirring until there is obtained a second homogenized mixture. This second homogenized mixture then is treated by a well-known calendering process or extrusion process to provide a film.

In the examples 1 and 2, S-PVC is used in the form of powder. The plasticizer, SnS stabilizer and tris(nonylphenyl) phosphite are added in form of a homogenized, liquid mixture. The further added ingredients of the recipe are added in form of a homogenized solid mixture. Mixing is continued until there is obtained a mixture with uniform distribution of the ingredients, i.e. complete homogenization. 

What is claimed is:
 1. Method for producing plastic materials characterized by the following steps:(a) heating PVC or S-PVC in a heating vessel while stirring, adding plasticizer, SnS stabilizer and tris(nonylphenyl) phosphite and continuing stirring to produce a first homogenized mixture; (b) cooling said first homogenized mixture to room temperature to obtain a purlable sandy product; (c) then adding mixtures of acrylate rubber and PVC and acrylate rubber and styrene monomer, styrene, polyethylene wax, tris(hydroxyethyl) isocyanurate and octadecyl 3-(3.5-4 hydroxyphenyl propionate) and stirring the mixture in said heating vessel to produce a second homogenized mixture; (d) calendering or extruding said second homogenized mixture to produce a film.
 2. Method according to claim 1, characterized in that said PVC or S-PVC is heated in step (a) to 120° C.
 3. Method according to claim 1, characterized in that said plasticizer, SnS stabilizer and tris(nonylphenyl) phosphite are added in form of a homogenized liquid mixture.
 4. Method for producing plastic materials characterized by the following steps:(a) heating PVC or S-PVC in a heating vessel while stirring, adding plasticizer, SnS stabilizer and tris(nonylphenyl) phosphite and continuing stirring to produce a first homogenized mixture; (b) cooling said first homogenized mixture to room temperature to obtain a purlable sandy product; (c) then adding mixtures of acrylate rubber and PVC, polystyrene/polyethylene-butylene block copolymer, polyethylene wax, tris(hydroxyethyl) isocyanurate and octadecyl 3-(3.5-4 hydroxyphenyl propionate) and stirring the mixture in said heating vessel to produce a second homogenized mixture; (d) calendering or extruding said second homogenized mixture to produce a film.
 5. Method according to claim 4, characterized in that said PVC or S-PVC is heated in step (a) at 120° C.
 6. Method according to claim 4, characterized in that said plasticizer, SnS stabilizer and tris(nonylphenyl) phosphite are added in form of a homogenized liquid mixture. 